I downloaded the test sketch but keep getting the message from my MAC OS X 10.5.8 that "there is no default application specified to open the document "arduino_test.pde"" What is the application needed, and how do I find it? What am I doing wrong?

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1.0 switched to using .ino as the file extension. So PDE may not be associated with the Arduino IDE. The suggestion to use "File -> Open" was from inside of the Arduino IDE and not Finder. Try opening the PDE from inside the Arduino IDE or right-click on the .PDE file and select "Open With...".

I opened the Arduino IDE and tried to open arduino_test.pde within the IDE, but when I clicked to open, the message was that there is no default application to open arduino_test.pde. When I right clicked on arduino_test.pde, I clicked onto "open with". I was given the option to choose an application. When I clicked on Arduino as the application, I could not go any further. The only option was to cancel. How can I designate the application?